On October 23rd, 2014, the Moon will pass in front of the sun, off-center, producing a partial solar eclipse visible in most of the United States
Sunsets are always pretty. One sunset this month could be out of this world. On Thursday, Oct. 23rd, the setting sun across eastern parts of the USA will be red, beautiful and - crescent-shaped.
It's a partial solar eclipse. In other words, the New Moon is going to 'take a bite' out of the sun.
A total eclipse is when the Moon passes directly in front of the sun, completely hiding the solar disk and allowing the sun's ghostly corona to spring into view. A partial eclipse is when the Moon passes in front of the sun, off-center, with a fraction of the bright disk remaining uncovered.
The partial eclipse of Oct. 23rd will be visible from all of the United States except Hawaii and New England. Coverage ranges from 12% in Florida to nearly 70% in Alaska. Weather permitting, almost everyone in North America will be able to see the crescent.
The eclipse will be especially beautiful in eastern parts of the USA, where the Moon and sun line up at the end of the day, transforming the usual sunset into something weird and wonderful.
Observers in the Central Time zone have the best view because the eclipse is in its maximum phase at sunset. They will see a fiery crescent sinking below the horizon, dimmed to human visibility by low-hanging clouds and mist.
Warning: Don't stare. Even at maximum eclipse, a sliver of sun peeking out from behind the Moon can still cause pain and eye damage. Direct viewing should only be attempted with the aid of a safe solar filter.
During the eclipse, don't forget to look at the ground. Beneath a leafy tree, you might be surprised to find hundreds of crescent-shaped sunbeams dappling the grass. Overlapping leaves create a myriad of natural little pinhole cameras, each one casting an image of the crescent-sun onto the ground beneath the canopy. When the eclipsed sun approaches the horizon, look for the same images cast on walls or fences behind the trees.
Here's another trick: Criss-cross your fingers waffle-style and let the sun shine through the matrix of holes. You can cast crescent suns on sidewalks, driveways, friends, cats and dogs-you name it. Unlike a total eclipse, which lasts no more than a few minutes while the sun and Moon are perfectly aligned, the partial eclipse will goes on for more than an hour, plenty of time for this kind of shadow play.
A partial eclipse may not be total, but it is totally fun.
Return Of The Blue Marble
The Deep Space Climate Observatory, a NOAA mission that carries NASA instruments, is providing a "new and complementary" view of Earth that is amazing scientists and lay people alike.
The Period Of The Solar Minimum
Intense solar activity such as sunspots and solar flares subsides during solar minimum, but that doesn't mean the sun becomes dull. Solar activity simply changes form
High up in the clear blue noontime sky, the sun appears to be much the same day-in, day-out, year after year.
But astronomers have long known that this is not true. The sun does change. Properly-filtered telescopes reveal a fiery disk often speckled with dark sunspots. Sunspots are strongly magnetized, and they crackle with solar flares-magnetic explosions that illuminate Earth with flashes of X-rays and extreme ultraviolet radiation. The sun is a seething mass of activity.
Until it's not. Every 11 years or so, sunspots fade away, bringing a period of relative calm.
This is called solar minimum and it's a regular part of the sunspot cycle.
The sun is heading toward solar minimum now. Sunspot counts were relatively high in 2014, and now they are sliding toward a low point expected in 2019-2020.
While intense activity such as sunspots and solar flares subside during solar minimum, that doesn't mean the sun becomes dull. Solar activity simply changes form.
For instance, during solar minimum we can see the development of long-lived coronal holes.
Coronal holes are vast regions in the sun's atmosphere where the sun's magnetic field opens up and allows streams of solar particles to escape the sun as the fast solar wind.
We see these holes throughout the solar cycle, but during solar minimum, they can last for a long time - six months or more. Streams of solar wind flowing from coronal holes can cause space weather effects near Earth when they hit Earth's magnetic field. These effects can include temporary disturbances of the Earth's magnetosphere, called geomagnetic storms, auroras, and disruptions to communications and navigation systems.
During solar minimum, the effects of Earth's upper atmosphere on satellites in low Earth orbit changes too.
Normally Earth's upper atmosphere is heated and puffed up by ultraviolet radiation from the sun. Satellites in low Earth orbit experience friction as they skim through the outskirts of our atmosphere. This friction creates drag, causing satellites to lose speed over time and eventually fall back to Earth. Drag is a good thing, for space junk; natural and man-made particles floating in orbit around Earth. Drag helps keep low Earth orbit clear of debris.
But during solar minimum, this natural heating mechanism subsides. Earth's upper atmosphere cools and, to some degree, can collapse. Without a normal amount of drag, space junk tends to hang around.
There are unique space weather effects that get stronger during solar minimum. For example, the number of galactic cosmic rays that reach Earth's upper atmosphere increases during solar minimum. Galactic cosmic rays are high energy particles accelerated toward the solar system by distant supernova explosions and other violent events in the galaxy.
During solar minimum, the sun's magnetic field weakens and provides less shielding from these cosmic rays. This can pose an increased threat to astronauts traveling through space.
Solar minimum brings about many changes to our sun, but less solar activity doesn't make the sun and our space environment any less interesting.
For more news about the changes ahead, stay tuned
Bright Explosion on the Moon
Astrophysics researchers who monitor the Moon for meteoroid impacts have detected the brightest explosion in the history of their program.
For the past 8 years, astronomers have been monitoring the Moon for signs of explosions caused by meteoroids hitting the lunar surface. Lunar meteor showers have turned out to be more common than anyone expected, with hundreds of detectable impacts occurring every year.
They've just seen the biggest explosion in the history of the program.
On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium. It exploded in a flash nearly 10 times as bright as anything we've ever seen before.
Anyone looking at the Moon at the moment of impact could have seen the explosion--no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.
Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the impact in a digital video recorded by one of the monitoring program's 14-inch telescopes. It jumped right out at me, it was so bright, he recalls.
The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph. The resulting explosion1 packed as much punch as 5 tons of TNT.
The lunar impact might have been part of a much larger event.
On the night of March 17, University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth. These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt.
This means Earth and the Moon were pelted by meteoroids at about the same time.
"My working hypothesis is that the two events are related, and that this constitutes a short duration cluster of material encountered by the Earth-Moon system.
One of the goals of the lunar monitoring program is to identify new streams of space debris that pose a potential threat to the Earth-Moon system. The March 17th event seems to be a good candidate.
Controllers of Lunar Reconnaissance Orbiter have been notified of the strike. The crater could be as wide as 20 meters, which would make it an easy target for LRO the next time the spacecraft passes over the impact site. Comparing the size of the crater to the brightness of the flash would give researchers a valuable ground truth measurement to validate lunar impact models.
Unlike Earth, which has an atmosphere to protect it, the Moon is airless and exposed. Lunar meteors crash into the ground with fair frequency. Since the monitoring program began in 2005, astronomers associated with lunar impact has detected more than 300 strikes, most orders of magnitude fainter than the March 17th event. Statistically speaking, more than half of all lunar meteors come from known meteoroid streams such as the Perseids and Leonids. The rest are sporadic meteors--random bits of comet and asteroid debris of unknown parentage.
U.S. Space Exploration Policy eventually calls for extended astronaut stays on the lunar surface. Identifying the sources of lunar meteors and measuring their impact rates gives future lunar explorers an idea of what to expect. Is it safe to go on a moonwalk, or not? The middle of March might be a good time to stay inside.
We'll be keeping an eye out for signs of a repeat performance next year when the Earth-Moon system passes through the same region of space. "Meanwhile, our analysis of the March 17th event continues."
The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.
